Multilayer solid golf ball

ABSTRACT

A multilayer solid golf ball may include a core formed from a highly neutralized polymer and a cover surrounding the core. The ball may also include an enclosing layer disposed between the core and the cover, the enclosing layer having a thermal conductivity of 0.12 W/m-K or less.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/230,272, published as U.S. Patent Application Publ. No.2010/0056302, entitled “Multilayer Solid Golf Ball,” the entiredisclosure of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a golf ball and, more particularly, toa multilayer solid golf ball having an enclosing layer with a lowthermal conductivity therein.

BACKGROUND OF THE INVENTION

A golfer typically selects a golf ball that has a combination offeatures based on his or her preferences and/or skill. Golf balldesigners often attempt to provide a ball with characteristics that arebalanced to suit a variety of golfer preferences and/or skill.Frequently, golf balls include a plurality of layers, with each layerhelping to provide one or more desired qualities.

Flying distance is an important index by which a golf ball may beevaluated. The three main factors affecting flying distance of a golfball are “initial velocity,” “spin rate,” and “launch angle.” Initialvelocity is one of the primary physical properties affecting the flyingdistance of a golf ball. The coefficient of restitution (COR) is analternate parameter indicative of the initial velocity of a golf ball.Typically, the COR of a golf ball varies with temperature. Taking 24degrees Celsius as the standard temperature, the physical properties,including the COR, of a golf ball will be affected when the temperatureof the ball is lower than 24 degrees Celsius. The COR is typicallysignificantly positive relative to the temperature, so the golf ballusually flies shorter in colder weather.

When playing golf in cold weather, 0 degrees Celsius for example, agolfer may utilize one or more techniques and, in some cases, heatingdevices to warm the ball. For example, in some cases, a golfer may usebody temperature (for instance by putting the ball in their pocket orholding it in their hand) or a golf ball heater to raise the temperatureof the golf ball in order to raise the COR of the golf ball therebyenabling the golfer to drive the ball farther. However, such warmingtechniques typically do not keep the temperature of the golf ball raisedfor a long time. Therefore, the raised COR of the golf ball cannot bekept elevated for a long time by using above-mentioned techniques. Thatis, the temperature will drop quickly when the ball leaves the golfer'sbody or the golf ball heater, and the temperature drop will result in anundesired deterioration of the COR of the ball, for example before theplayer has completed their round of golf. This often results in suddenchanges of the COR that make it difficult for the golfer to predict andcontrol the flying distance of the ball. Therefore, it would bedesirable to reduce the effect of low temperature on the COR of a golfball, and thus provide a ball that may maintain a desirable COR for asustained amount of time in order to enable a golfer to complete a roundor several holes without the COR dropping to undesired levels.

The present disclosure is directed to improvements in the consistency ofgolf ball performance characteristics across a broader range of playingconditions.

SUMMARY OF THE INVENTION

An objective of the present invention is to provide a multilayer solidgolf ball, which has better properties with respect to flying distanceand ball control in cold weather. To achieve this objective, anexemplary multilayer solid golf ball may include a core having a CORgreater than 0.75 at a standard temperature of about 24 degrees Celsius,a cover surrounding the core, and an enclosing layer between the coreand the cover. The enclosing layer may have a relatively low thermalconductivity, for example less than or equal to 0.2 W/m-K. Because ofthe relatively low thermal conductivity of the enclosing layer, it maylimit the transfer of heat to and from the core. Thus, the enclosinglayer may improve the sustainability of a desirable COR in cold weatherconditions by limiting the deterioration in the COR of the ball undersuch conditions. This may maintain a desirable level of ballcontrollability as well as flying distance.

In one aspect, the present disclosure is directed to a multilayer solidgolf ball. The ball may include a core formed from a highly neutralizedpolymer and a cover surrounding the core. The ball may also include anenclosing layer disposed between the core and the cover, the enclosinglayer having a thermal conductivity of 0.12 W/m-K or less.

In another aspect, the present disclosure is directed to a multilayersolid golf ball. The ball may include a core having a coefficient ofrestitution greater than 0.75 at a temperature of 24° C., wherein thecore is formed from a highly neutralized polymer and a cover surroundingthe core. In addition, the ball may also include an insulating layerdisposed between the core and the cover, and having a thermalconductivity that is lower than the thermal conductivity of the cover.

In another aspect, the present disclosure is directed to a multilayersolid golf ball. The ball may include a core having a coefficient ofrestitution greater than 0.75 at a temperature of 24° C. and having aShore D hardness in the range of about 30 to 60. The ball may alsoinclude a cover surrounding the core. In addition the ball may includean enclosing layer disposed between the core and the cover, theenclosing layer having a thermal conductivity of 0.12 W/m-K or less.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one of ordinary skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description and this summary, bewithin the scope of the invention, and be protected by the followingclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereference numerals designate corresponding parts throughout thedifferent views.

FIG. 1 shows a cross-sectional view of an exemplary golf ball inaccordance with this disclosure, the golf ball being of a four-piececonstruction;

FIG. 2 shows a cross-sectional view of an alternative golf ball having afour-piece construction;

FIG. 3 shows a cross-sectional view of an exemplary golf ball inaccordance with this disclosure, the golf ball being of a five-piececonstruction including a mantle layer; and

FIG. 4 shows a cross-sectional view of an alternative golf ball inaccordance with this disclosure, the golf ball being of a five-piececonstruction including a mantle layer.

DETAILED DESCRIPTION

The present disclosure is directed to a golf ball formed of materialsand layers with certain performance characteristics. The followingparagraphs explain the measurement processes for severalcharacteristics.

For purposes of this disclosure, the term “compression deformation”refers to the amount deformation exhibited by an object when compressedunder a predetermined set of loading parameters. As used in the presentdisclosure, compression deformation shall refer to the deformationamount (in millimeters) of an object when compressed by a force,specifically, the deformation of the object when the compression forceis increased from 10 kg to 130 kg. The deformation amount of the objectunder the force of 10 kg is subtracted from the deformation amount ofthe object under the force of 130 kg to obtain the compressiondeformation value of the object. While compression deformation is aparameter that may be measured for entire golf balls, compressiondeformation can also be measured for individual components of golfballs. In the present disclosure, compression deformation of a golf ballinner core layer, which, like the entire golf ball, may also bespherical, is measured and discussed in detail.

Hardness of a golf ball layer is measured generally in accordance withASTM D-2240. In some cases the hardness may be measured on across-sectional surface of a ball layer. In other cases, the hardnessmay be measured on the curved surface of a ball layer. When measuringthe hardness of a golf ball as a whole the measurement is taken on theland area of the outer surface of the ball.

Flexural modulus of a golf ball material is measured in accordance withASTM D-790.

Coefficient of restitution (COR), as referred to in the presentdisclosure, is measured in the following manner. To measure COR, a golfball is fired by an air cannon, or other propulsion device, at aninitial velocity of 40 m/sec toward a steel plate located about 1.2meters away from the cannon. A speed monitoring device is located at adistance of 0.6 to 0.9 meters from the cannon. The speed monitoringdevice measures the speed of the golf ball after bouncing off the steelplate. The return velocity divided by the initial velocity is the COR.

For the purposes of this disclosure, the term “thermoplastic” refers tothe conventional meaning of the term thermoplastic, i.e., a composition,compound, material, medium, substance, etc., which exhibits the propertyof a material, such as a high polymer, that softens when exposed to heatand generally returns to its original condition when cooled to roomtemperature (e.g., at from about 20° to about 25° C.)

For the purposes of this disclosure, the term “thermoset” refers to theconventional meaning of the term thermoset, i.e., a composition,compound, material, medium, substance, etc., that is cross-linked suchthat it does not have a melting temperature, and cannot be dissolved ina solvent, but which may be swelled by a solvent.

For the purposes of this disclosure, the term “polymer” refers to amolecule having more than 30 monomer units, and which may be formed orresult from the polymerization of one or more monomers or oligomers.

For the purposes of this disclosure, the term “oligomer” refers to amolecule having 2 to 30 monomer units.

For the purposes of this disclosure, the term “monomer” refers to amolecule having one or more functional groups and which is capable offorming an oligomer and/or polymer.

For the purposes of this disclosure, the term “ionomer” refers to amonomer having at least one carboxylic acid group, and which may be atleast partially or completely neutralized by one or more bases(including mixtures of bases) to provide carboxylic acid salt monomers(or mixtures of carboxylic acid salt monomers). For example, the ionomermay comprise a mixture of carboxylic acid sodium and zinc saltsmonomers, such as the mixed ionomer used in making the ionomer resinsold under DuPont's trademark SURLYN® for cut-resistant golf ballcovers.

For the purposes of this disclosure, the term “ionomer resin” refers toan oligomer or polymer which may comprise, or be formed, from one ormore ionomer units or ionomers, and which may be a copolymer of one ormore ionomers (such as methacrylic acid which is at least partially orcompletely neutralized) and one or more monomers or oligomers which isnot an ionomer, such as, for example, ethylene.

For the purposes of this disclosure, the term highly neutralized polymerrefers to polymers whose charge has been mostly countered by theaddition of a counter-ion material. Highly neutralized polymers may havea charge dissipation of 95% or greater.

For the purposes of this disclosure, the term “elastomer” refers tooligomers or polymers having the property of elasticity, and may be usedinterchangeably with the term “rubber” herein.

For the purposes of this disclosure, the term “polyisocyanate” refers toan organic molecule having two or more isocyanate functional groups(e.g., a diisocyanate). Polyisocyanates useful herein may be aliphaticor aromatic, or a combination of aromatic and aliphatic, and mayinclude, but are not limited to, diphenyl methane diisocyanate (MDI),toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI),dicyclohexylmethane diisocyanate (H12MDI), isoprene diisocyanate (IPDI),etc.

For the purposes of this disclosure, the term “polyol” refers to anorganic molecule having two or more hydroxy functional groups. The term“polyol” may include diols, triols, etc., polyester polyols, polyetherpolyols, polycarbonate diols, etc. For example, these other polyols mayinclude “bio-renewable” polyether polyols (i.e., those polyether polyolswhich have reduced impact on the environment during processing) such asone or more of polytrimethylene ether glycol, polytetramethylene etherglycol (PTMEG), etc., which have, for example, a hydroxyl value of 11.22to 224.11 mg KOH/g. These “bio-renewable” polyether polyols, such aspolytrimethylene ether glycols, may be derived, obtained, extracted,etc., from bio-renewable resources, such as through a fermentationprocess of natural corn, rather by a synthetic chemical process.

For the purposes of this disclosure, the term “polyurethane” refers to apolymer which is joined by urethane (carbamate) links, and which may beprepared, for example, from polyols (or compounds forming polyols suchas by ring-opening mechanisms, e.g., epoxides) and polyisocyanates.Polyurethanes useful herein may be thermoplastic or thermosetting, butare thermoplastic when used in the cover. The soft segment of athermoplastic polyurethane may also be partially cross-linked with otherpolyols or materials to achieve varying properties or characteristics,such as to manipulate the hardness, etc.

For the purposes of this disclosure, the term “chain extender” refers toan agent which increases the molecular weight of a lower molecularweight polyurethane to a higher molecular polyurethane. Chain extendersmay include one or more diols such as ethylene glycol, diethyleneglycol, butane diol, hexane diol, etc.; triols such as trimethylolpropane, glycerol, etc.; and polytetramethylene ether glycol, etc.

The present disclosure is directed to golf ball layers having certainperformance characteristics. These characteristics may be achieved dueto the structural configuration of the layers and/or the materialcompositions of the layers. Further, the overall performancecharacteristics of the golf ball are affected in certain ways by themakeup of individual layers and also reflect the combination andarrangement of the layers and materials from which the golf ball isformed. Accordingly, the dimensions and materials of each layer may beselected to achieve desired performance characteristics.

The concepts discussed in the present disclosure may be applicable togolf balls having any construction, having any suitable number oflayers. In some embodiments, an exemplary golf ball having the disclosedperformance characteristics may have a four-piece or four-layerconstruction. In other embodiments, the ball may have a five-piececonstruction. In addition, other configurations are envisioned thatinclude six or more layers.

Further, although the disclosure describes various embodiments relatingto golf balls, a person having ordinary skill in the art will be able toadapt the disclosed concepts for use in other types of balls (other thangolf balls) and for use in other types of layered articles. For example,the disclosed concepts may be applicable to any layered article, such asa projectile, ball, recreational device, or individual components ofthese articles.

In accordance with the present disclosure, a golf ball may includeprovisions to limit the deterioration of the COR of the ball's core incold weather. For example, in some embodiments, an exemplary golf ballmay include an insulating layer enclosing the core. The insulating layer(or enclosing layer) may have a relatively low thermal conductivity inorder to limit heat transfer between the core and the atmosphericenvironment. That is, the insulating layer may limit the conduction ofheat from the core to other portions of the ball and, ultimately, to theatmospheric air. With such an insulating layer, the core may take alonger time to cool down in cold weather, and thus, may maintain ahigher COR.

As shown in FIG. 1, a multilayer solid golf ball 100 may include a core10, a cover 20, an intermediate layer 30, and an enclosing layer 40. Asshown in FIG. 1, in some embodiments, ball 100 may have a four-piececonstruction. The disclosed concepts may be applicable to four-piecegolf balls, such as ball 100, as well as balls having otherconfigurations, such as five-piece constructions, six-piececonstructions, or constructions having any suitable number of pieces,including embodiments having more than six layers.

In some embodiments, golf ball 100 may have a diameter of at least 42.67mm (1.680 inches), in accordance with the Rules of Golf. For example, insome embodiments, golf ball 100 may have a ball diameter between about42.67 mm and about 42.9 mm, and may, in some embodiments, have a balldiameter of about 42.7 mm. Golf ball 100 may have a ball weight betweenabout 45 g and about 45.8 g and may, in some embodiments, have a ballweight of about 45.4 g. The golf ball may be ‘conforming,’ i.e., inconformance with the USGA rules about golf balls, including weight,diameter, initial velocity, and the like, or it may be ‘non-conforming.’The specifications set forth in this paragraph may be applicable to allgolf ball embodiments described in the present disclosure.

Core

Core 10 may be disposed at the most central portion of ball 100.Accordingly, core 10 may be spherical with an outer surface 11. In somecases, such a component may be referred to as a central core, innercore, or inner core layer. In addition, although core 10 is shown anddiscussed in the present disclosure as having a single layerconstruction, in some embodiments, core 10 may have a multilayerconstruction.

Core 10 may be made, for example, by hot-press molding or injectionmolding. In some embodiments, injection molding may be preferred. Duringan exemplary injection molding process of forming core 10, thetemperature of the injection machine may be set in a range ofapproximately 190° C. to 220° C.

Core Dimensions

Core 10 may have a diameter in a range between 19 mm and 37 mm, with apreferred diameter range of between 21 mm and 35 mm, more typicallybetween approximately 24 mm and approximately 28 mm. In someembodiments, core 10 may have a diameter of approximately 24.5 mm (forexample, 24.5+/−0.15). In some embodiments, core 10 may have a diameterof 24.5 mm.

Core Properties

As noted above, the COR of a golf ball is a significant factorcontributing to the flying distance of the ball. COR is a ratio of thespeed of the ball after a collision of particular conditions to thespeed of the ball before the collision. Thus, the COR of a ball is avalue that quantifies the elasticity of the ball during collisionsbetween the ball and other objects, such as a golf club. The higher theCOR, the faster the initial velocity of the ball will be coming off theclubface. In some embodiments, core 10 may have a COR greater than 0.75,preferably greater than 0.77, more preferably greater than 0.79, andmost preferably greater than 0.8.

Golf ball 100, as a whole, may have a COR of approximately 0.776. Forexample, in some embodiments, ball 100 may have a COR of 0.776+/−0.004.In some embodiments, ball 100 may have a COR of 0.776.

In addition to COR, other properties may be desirable for the core. Forexample, it may be desirable for the core to have a certain hardnessand/or specific gravity.

In some embodiments, core 10 may have a surface Shore D hardness in therange of about 30 to 60, preferably in the range of about 45 to 55. Insome embodiments, core 10 may have a surface shore D hardness ofapproximately 50 (for example 50+/−2). In some embodiments, core 10 mayhave a surface shore D hardness of 50. To provide golf ball 100 withstable performance, core 10 may have a Shore D cross-sectional hardnessof from 45 to 55 at any single point on a cross-section obtained bycutting core 10 in half. Further, core 10 may have a Shore Dcross-sectional hardness difference between any two points on thecross-section of within +/−6 and, in some embodiments, the differencebetween any two points on the cross-section may be within +/−3.

Certain attributes of the golf ball, such as moment of inertia, may bedetermined, in part, by the comparative physical properties of thedifferent layers of the golf ball. For example, in some embodiments, agreater moment of inertia may be achieved by forming layers disposedradially outward from the center of the ball with a higher specificgravity, and by forming layers disposed radially inward toward thecenter of the ball with a relatively lower specific gravity. A golf ballwith a greater moment of inertia may maintain its rate of spin forlonger than a golf ball with a lower moment of inertia. This may providea ball with improved short game characteristics, as spin enables aplayer to hit a ball near the hole with limited roll beyond the point ofimpact and, in some cases, even roll backward after landing. Spin mayalso contribute to longer drives, as the trajectory will not drop off assteeply as the ball starts coming back down after reaching its apex.

In some embodiments, it may be desirable for golf ball 100 to have amoment of inertia between about 82 g-cm² and about 90 g-cm². Such amoment of inertia may produce desirable distance, trajectory, andcontrol. Such a moment of inertial may produce desirable performancecharacteristics, for example, when golf ball 100 is struck with a driverand/or is flying against the wind. To provide golf ball 100 with agreater moment of inertia, core 10 may have a lower specific gravitythan outer layers. In some embodiments, the specific gravity of core 10may be in the range of about 0.9 g/cm³ to about 1.1 g/cm³. For example,in some embodiments, the specific gravity of core 10 may beapproximately 1.07 (for example 1.07+/−0.02). In some embodiments, thespecific gravity of core 10 may be 1.07.

Another parameter that can have an affect on the performance of the ballis the compression deformation. Compression deformation is a physicalparameter that may be quantified (in millimeters for example) accordingto the measurement protocol set forth above. A higher compressiondeformation value indicates that the ball deforms more when subjected toa given compressive force. That is, a ball having a higher compressiondeformation is more compressible than a ball having a lower compressiondeformation. In some embodiments, core 10 may have a compressiondeformation value in a range of about 2 mm to about 5 mm at 24° C. Insome embodiments, core 10 may have a compression deformation value inthe range from about 3 mm to about 5 mm.

Core Materials

The core and other components of the golf ball may be formed from anymaterials suitable for providing the component and the ball as a wholewith the desired properties and performance characteristics. Exemplarysuch materials are described below. In addition, exemplary suitablematerials are also discussed in U.S. patent application Ser. No.13/193,289, filed Jul. 28, 2011, entitled “Golf Balls Including ACrosslinked Thermoplastic Polyurethane Cover Layer Having Improved ScuffResistance,” the entire disclosure of which is incorporated herein byreference.

Core 10 may be formed of a relatively firm material in order to providea long flying distance. In some embodiments, the core 10 may be madefrom a thermoplastic or thermosetting material, with a thermoplasticmaterial preferred. When the core 10 is made from a thermoplasticcomposition, the thermoplastic composition may have a flexural modulusin a range of from 5 kpsi to 70 kpsi, preferably from 5 kpsi to 60 kpsi,more preferably from 5 kpsi to 50 kpsi and most preferably from 5 kpsito 45 kpsi. The thermoplastic material of core 10 may include an ionomerresin, polyamide resin, polyester resin, polyurethane resin, or amixture of these or other such resins.

In some embodiments, an ionomer resin may be preferred for core 10. Forexample, in some embodiments, core 10 may be formed, at least in part,from a highly neutralized polymer. The polymer may be neutralized to 70percent or higher, including up to 100 percent, with a suitable cationsource, such as magnesium, sodium, zinc, or potassium. In someembodiments, the polymer may preferably be neutralized to 80 percent orhigher. Suitable highly neutralized polymers for use in forming core 10may include a highly neutralized polymer and optionally additives,fillers, and/or melt flow modifiers. Suitable highly neutralized polymercompositions include salts of homopolymers and copolymers ofα,β-ethylenically unsaturated mono- or dicarboxylic acids, andcombinations thereof, optionally including a softening monomer.

Suitable highly neutralized polymer compositions may include HPF resinssuch as HPF1000, HPF2000, HPF AD1027, HPF AD1035, HPF AD1040, andmixtures thereof, all produced by E. I. Dupont de Nemours and Company.Suitable highly neutralized polymer compositions for use in forming aninner core may comprise a highly neutralized polymer composition andoptionally additives, fillers, and/or melt flow modifiers.

Suitable additives and fillers include, for example, blowing and foamingagents, optical brighteners, coloring agents, fluorescent agents,whitening agents, UV absorbers, light stabilizers, defoaming agents,processing aids, mica, talc, nanofillers, antioxidants, stabilizers,softening agents, fragrance components, plasticizers, impact modifiers,acid copolymer wax, surfactants; inorganic fillers, such as zinc oxide,titanium dioxide, tin oxide, calcium oxide, magnesium oxide, bariumsulfate, zinc sulfate, calcium carbonate, zinc carbonate, bariumcarbonate, mica, talc, clay, silica, lead silicate, and the like; highspecific gravity metal powder fillers, such as tungsten powder,molybdenum powder, and the like; regrind, i.e., core material that isground and recycled; and nano-fillers.

Any suitable melt flow modifiers may be included in the highlyneutralized polymer. Exemplary suitable melt flow modifiers may include,for example, fatty acids and salts thereof, polyamides, polyesters,polyacrylates, polyurethanes, polyethers, polyureas, polyhydricalcohols, and combinations thereof.

The highly neutralized polymer may also be mixed with conventionalionomers including, for example, Surlyn®, commercially available from E.I. Dupont de Nemous and Company, or IOTEK®, commercially available fromExxon Corporation. To achieve the desired COR, a main composition of thecore 10 is preferably HPF, and Surlyn® and/or IOTEK® aresub-compositions which are optionally added therein. The sub-compositionof core 10 is in an amount of 0 to 10 parts by weight, based on 100parts by weight of the main composition of the core 10.

In addition, or as an alternative, to one or more of the materialsdiscussed above, any other suitable materials may be also used to makethe core 10. A skilled artisan may recognize other suitable materialsfor providing core 10 with the desired properties and performancecharacteristics.

Cover

The outer surface of cover 20 may have a plurality of dimples configuredto provide a desired aerodynamic effect. The dimples may be arranged inany suitable dimple pattern. In some embodiments, golf ball 100 may beprovided with a dimple pattern including a total number of dimplesbetween approximately 300 and 400. For example, in some embodiments,ball 100 may have 360 dimples.

Cover Dimensions

The thickness of the cover 20 may be in a range of from 0.5 mm to 2.5mm, or in a range of from 0.8 mm to 2 mm, or in a range of from 1 mm to2 mm. Cover 20 may include one or more layers, and may also have one ormore finish coatings applied to its outer surface.

Cover Properties

Cover 20 may be formed of a relatively soft but durable material. Forexample, cover 20 may be formed of a material that compresses/flexeswhen struck by a golf club, in order to provide spin of the ball andfeel to the player. Although relatively soft, the material may also bedurable, in order to withstand scuffing from the club and/or the golfcourse. Exemplary cover layer materials may include urethane, ionomerblends, or any other suitable material, including blends. In addition,in some embodiments, cover 20 may include one or more cross-linkingagents.

Cover 20 has a Shore D hardness of from 25 to 80. In some embodiments,the Shore D hardness of cover 20 is higher than that of core 10 and insome embodiments, the Shore D hardness of cover 20 is higher than thatof core 10 by at least 10 points. In some embodiments, the Shore Dhardness of core 10 is higher than that of cover 20 and in someembodiments, the Shore D hardness of core 10 is higher than that ofcover 20 by at least 5 points. In some embodiments, cover 20 may have asurface Shore D hardness of approximately 54 to 61. In some embodiments,cover 20 may have a Shore D hardness of approximately 56 (for example56+/−2). In some embodiments, cover 20 may have a Shore D hardness of56.

Cover Materials

Any suitable thermoplastic or thermoset material may be used to makecover 20. In some embodiments, cover 20 may be made from a thermoplasticmaterial comprising at least one of an ionomer resin, a highlyneutralized polymer composition, a polyamide resin, a polyester resin, apolyurethane resin, and a combination thereof. In the presentembodiment, ionomer resin, polyurethane resin, or highly neutralizedpolymer composition is preferred for cover 20. In some embodiments,cover 20 is made from a thermoset material comprising at least one ofpolyurethane elastomers, polyamide elastomers, polyurea elastomers,diene-containing polymer, crosslinked metallocene catalyzed polyolefin,silicone, and a combination thereof. Among these thermoset materials,thermoset polyurethane elastomers are popular. When cover 20 is madefrom a thermoplastic material, the thermoplastic composition has aflexural modulus in a range of from 0.3 kpsi to 70 kpsi, or from 0.5kpsi to 60 kpsi, or from 1 kpsi to 50 kpsi, or from 1 kpsi to 40 kpsi.In some embodiments, cover 20 has a flexural modulus higher than that ofcore 10 and in some embodiments, cover 20 has a flexural modulus higherthan that of core 10 by at least 10 kpsi. In some embodiments, core 10has a flexural modulus higher than that of cover 20 and in someembodiments, core 10 has a flexural modulus higher than that of cover 20by at least 5 kpsi.

Intermediate Layer

Intermediate layer 30 may have an inner surface 31 and an outer surface32. In some embodiments, inner surface 31 may face enclosing layer 40and outer surface 32 may face cover 20, as shown in FIG. 1. In somecases, intermediate layer 30 may be referred to as an outer core, outercore layer, or mantle layer.

Intermediate Layer Dimensions

The thickness of the intermediate layer 30 may be in a range between 2mm and 11 mm, or in a range of 2.1 mm and 9.5 mm, or in a range between3.6 mm and 8.5 mm. Intermediate layer 30 is preferably made by hot-pressmolding. Suitable vulcanization conditions include a vulcanizationtemperature of between 130 degrees Celsius and 190 degrees Celsius, anda vulcanization time of between 5 and 20 minutes. To obtain the desiredrubber crosslinked body for use as intermediate layer 30 in the presentinvention, the vulcanizing temperature is preferably at least 140degrees Celsius.

Intermediate Layer Properties

Intermediate layer 30, may have a compression deformation value in arange of from 2.5 mm to 4.5 mm. In some embodiments, intermediate layer30 may have a compression deformation of approximately 3.05 (forexample, 3.05+/−0.25). In some embodiments, intermediate layer 30 mayhave a compression deformation of 3.05. In some embodiments, thecompression deformation value of intermediate layer 30 may be higher(i.e. more deformation) than the compression deformation value of core10. In some embodiments, the compression value of the intermediate layer30 may be lower (i.e. less deformation) than core 10. In someembodiments, the compression deformation of the combined structure ofintermediate layer 30, core 10, and enclosing layer 40 may beapproximately 3.2-3.3 mm.

Intermediate layer 30 may have a Shore D hardness in the range of 35 to65. In some embodiments, Intermediate layer 30 may have a Shore Dhardness of approximately 60 (for example 60+/−2). In some embodiments,intermediate layer 30 may have a Shore D hardness of 60. In someembodiments, the Shore D hardness of intermediate layer 30 may be lowerthan that of the core 10. In some embodiments, the Shore D hardness ofintermediate layer 30 may be higher than that of the core 10.

Intermediate Layer Materials

Intermediate layer 30 may be formed of a relatively firm and suitablyresilient material. Intermediate layer 30 may be configured to provide arelatively high launch and a relatively low spin rate when the ball isstruck by a driver, and a relatively higher spin rate and increasedcontrol when struck with irons. This may provide distance off the teeand control around the greens.

Intermediate layer 30 may be made from a thermoplastic material or athermosetting material. For example, in some embodiments, intermediatelayer 30 may comprise material selected from the following groups:

(1) thermoplastic materials selected from the group consisting ofionomer resin, highly neutralized polymer composition, polyamide resin,polyester resin, polyurethane resin and a mixture thereof; or (2)thermoset materials selected from the group consisting of polyurethaneelastomer, polyamide elastomer, polyurea elastomer, diene-containingpolymer (such as polybutadiene), crosslinked metallocene catalyzedpolyolefin, silicone, and mixtures thereof.

An intermediate layer made from thermoset materials may be made bycrosslinking a polybutadiene rubber composition. When other rubber isused in combination with a polybutadiene, it is typical thatpolybutadiene is included as a principal component. Specifically, aproportion of polybutadiene in the entire base rubber is preferablyequal to or greater than 50% by weight, and particularly preferablyequal to or greater than 80% by weight.

Exemplary base rubbers that may be used in the rubber compositioninclude 1,4-cis-polybutadiene, polyisoprene, styrene-butadienecopolymers, natural rubber, and a mixture thereof. To have a betterresilient performance, 1,4-cis-polybutadiene is preferred.Alternatively, cis-1,4-polybutadiene can be used as the base materialfor the intermediate layer 30 and mixed with other ingredients. However,the amount of cis-1,4-polybutadiene should be at least 50 parts byweight, based on 100 parts by weight of the rubber composition. Apolybutadiene having a proportion of cis-1,4 bonds of equal to orgreater than 60 mol %, and further, equal to or greater than 80 mol % istypical. In some embodiments, cis-1,4-polybutadiene may be used as thebase rubber and mixed with other ingredients.

In some embodiments, a polybutadiene synthesized using a rare earthelement catalyst may be used. Excellent resilience performance of a golfball may be achieved by using this polybutadiene. Examples of rare earthelement catalysts include lanthanum series rare earth element compounds.Other catalysts may include an organoaluminum compound, and alumoxaneand halogen containing compounds. A lanthanum series rare earth elementcompound is typical. Polybutadiene obtained by using lanthanum seriesrare earth-based catalysts usually employ a combination of lanthanumseries rare earth (atomic number of 57 to 71) compounds, butparticularly typical is a neodymium compound.

Various additives may be added to the base rubber to form a compound.The additives may include a cross-linking agent and a filler. In someembodiments, the cross-linking agent may be zinc diacrylate, magnesiumacrylate, zinc methacrylate, or magnesium methacrylate. In someembodiments, zinc diacrylate may provide advantageous resilienceproperties. The filler may be used to increase the specific gravity ofthe material. The filler may include zinc oxide, barium sulfate, calciumcarbonate, or magnesium carbonate. In some embodiments, zinc oxide maybe selected for its advantageous properties. Metal powder, such astungsten, may alternatively be used as a filler to achieve a desiredspecific gravity. In some embodiments, the density of an intermediatelayer may be from about 1.05 g/cm³ to about 1.25 g/cm³.

Enclosing Layer

Enclosing layer 40 may surround core layer 10. It should be noted thatany layer may surround or substantially surround any layers disposedradially inward of that layer. For example, cover 20 may surround orsubstantially surround intermediate layer 30.

Enclosing layer 40 may serve as an insulating layer configured to limitcooling of core 10 in cold weather. In some embodiments, enclosing layer40 may be located between core 10 and intermediate layer 30, as shown inFIG. 1. The extent to which enclosing layer 40 limits heat transfer fromcore 10 is dependent on the thickness of enclosing layer 40 and thethermal conductivity of the enclosing layer 40.

Enclosing Layer Dimensions

To maintain the COR of ball 100, the thickness of the enclosing layer 40may be less than or equal to 1 mm, or in a range between 0.005 mm and0.70 mm, or in a range between 0.01 mm and 0.4 mm. If the thickness ofthe enclosing layer 40 is less than 0.005 mm, the low thermalconductivity effect of the enclosing layer 40 is not significant. In thepresent embodiment, the enclosing layer 40 directly covers the outersurface 11 of the core 10. In other words, the enclosing layer 40 has aninner surface 41 contacting the outer surface 11 of core 10 and an outersurface 42 contacting the inner surface 31 of the intermediate layer 30.

Enclosing Layer Properties

In order to limit transfer of heat from core 10, enclosing layer 40 maybe made from a material with a relatively low thermal conductivity. Insome embodiments, the thermal conductivity of enclosing layer 40 may belower than the thermal conductivity of cover 20 and/or lower than thethermal conductivity of intermediate layer 30. In some embodiments, thethermal conductivity of enclosing layer 40 may be less than or equal to0.2 W/m-K so that the enclosing layer 40 will have a superiorperformance in reducing the conductivity of the cold from cover 20 tocore 10. In some embodiments, the thermal conductivity of enclosinglayer 40 is preferably between 0.04 W/m-K and 0.15 W/m-K, and morepreferably between 0.06 W/m-K and 0.15 W/m-K.

Enclosing Layer Materials

In some embodiments, the material of enclosing layer 40 may comprise atleast one of ethylene vinyl acetate (EVA), polyurethane, polyester,polyamide, polyisoprene, polyvinyl chloride (PVC), acrylonitrilebutadiene styrene, polyvinylidene fluoride, polyimide, and combinationsthereof. Those having ordinary skill in the art will recognize othermaterials having the properties desired for enclosing layer 40, such asa relatively low thermal conductivity.

In some embodiments, enclosing layer 40 may have a non-homogeneousstructure. For example, in some embodiments, enclosing layer 40 mayinclude particles embedded in a main layer material. The particles mayhave different properties than the main layer material and may bedistributed throughout the enclosing layer to provide the layer, as awhole, with certain desired characteristics. In other embodiments,enclosing layer 40 may be formed of a substantially homogeneousmaterial. That is, enclosing layer 40 may be comprised of a material ormaterials that are uniformly mixed to create a homogeneous composition.In some embodiments, a homogeneous enclosing layer formed of a materialhaving a relatively low thermal conductivity may provide morerestriction to heat transfer than, for example, a layer includingembedded particles having a low thermal conductivity. Embedded particlesmay not provide a fully encapsulating barrier to heat transfer in thesame way that a homogeneous layer of material having a low thermalconductivity.

Alternative Enclosing Layer Configuration

Although the enclosing layer 40 is disposed immediately adjacent innercore 10 in the embodiment shown in FIG. 1, the enclosing layer may bedisposed in any suitable location between core 10 and cover 20. Forexample, while the enclosing layer may, in some embodiments, be disposedradially inward of intermediate layer 30, as shown in FIG. 1, in otherembodiments, the enclosing layer may be disposed radially outward of theintermediate layer, as shown in FIG. 2.

FIG. 2 shows a multilayer solid golf ball 200 according to a secondembodiment, in which an alternate enclosing layer 80 is provided.Similar to ball 100 of the first preferred embodiment, ball 200 mayinclude a core 50, a cover 60, an intermediate layer 70, and enclosinglayer 80. As shown in FIG. 2, enclosing layer 80 may be disposed betweenintermediate layer 70 and cover 60. The enclosing layer 80 may have aninner surface 82 contacting an outer surface 71 of intermediate layer 70and an outer surface 81 contacting an inner surface 61 of cover 60.

The components of ball 200 may have substantially similarcharacteristics with corresponding components of ball 100. Accordingly,the descriptions of the components of ball 100 above may be applicableto the components of ball 200 as well.

In some embodiments, the dimensions and/or materials used for certaincomponents may vary with the placement of the components in order toachieve the same properties and performance characteristics. Forexample, in some embodiments, enclosing layer 80 may have a thicknessthat is slightly less than enclosing layer 40 due to its placementradially outward of intermediate layer 30 rather than radially inward ofintermediate layer 30. An enclosing layer that is located furtherradially outward will comprise more material than an inwardly disposedenclosing layer of the same thickness. Thus, the same amount ofinsulating material may be provided in an outwardly disposed insulatinglayer having a smaller thickness. This may provide a ball designer withmore flexibility to modify the dimensions of other components to achievedesired performance characteristics. On the other hand, an outwardlydisposed insulating layer will also have a greater surface area that maybe exposed to the cold, which may dictate that the insulating layer bethe same or greater thickness as an inwardly disposed insulating layer.Those having ordinary skill in the art will be able to determineappropriate changes to golf ball components to achieve similarperformance characteristics for balls having the insulating layers indifferent locations.

Mantle Layer

In some embodiments, at least one additional layer may be added to thegolf ball. For example, in some embodiments, a mantle layer may be addedbetween cover 20 and intermediate layer 30. Other layers may be added oneither side of any disclosed layer as desired to achieve certainperformance characteristics and/or attributes.

FIG. 3 illustrates a ball 101 having a similar construction andcomponents to ball 100. As shown in FIG. 3, ball 101 may further includea mantle layer 45. Mantle layer 45 may abut cover 20, as shown in FIG.3. Though referred to herein as a “mantle layer,” some of those in theart may refer to mantle layer 45 by other names, such as “inner coverlayer.” Regardless of the naming convention used, any layer positionednext to the outer cover, such as cover 20, may be considered a mantlelayer. As shown in FIG. 3, in some embodiments, mantle layer 45 may bedisposed radially outward of intermediate layer 30 and radially inwardof cover 20.

Mantle Dimensions

In some embodiments, mantle layer 45 may be thinner than cover 20. Thethickness of mantle layer 45 may be any thickness less than that ofcover 20. In some embodiments, the thickness of mantle layer 45 may beless than 1.2 mm. For example, in some embodiments, the thickness ofmantle layer 45 may be about 0.9 mm. In some embodiments, the thicknessof mantle layer 45 may be about 0.6 mm. In some embodiments, thethickness of mantle layer 45 may be approximately half of the thicknessof cover 20. In some embodiments, the thickness of mantle layer 45 maybe at least 0.3 mm less than the thickness of cover 20.

Mantle layer 45 may, in some embodiments, be the thinnest layer, or oneof the thinnest layers, in golf ball 101. One way to characterize thesize of mantle layer 45 is by the volume of the layer as a percentage ofthe total volume of golf ball 101. The total volume of golf ball 101 maybe considered to be the sum of the volumes of each of the layers of golfball 101. For example, because golf ball 101 comprises core 10,enclosing layer 40, intermediate layer 30, mantle layer 45, and cover20, the total volume of golf ball 101 is the sum of the core volume, theenclosing layer volume, the intermediate layer volume, the mantle layervolume, and the cover volume. Because each layer of the golf ball isspherical or a portion of a spherical body, the volume of any layer canbe calculated as the volume of a sphere having a diameter of thethickness of the layer or a portion of a sphere volume having a heightof the thickness of the layer.

In some embodiments of golf ball 101, mantle layer 45 may have a volumethat is 10 percent or less of the total volume of golf ball 101. In someembodiments where the thickness of mantle layer 45 is about 0.8 mm,mantle layer 45 may have a volume that is about 9.8 percent of the totalvolume of golf ball 101. In some embodiments where the thickness ofmantle layer 45 is about 0.6 mm, mantle layer 45 may have a volume thatis about 7.44 percent of the total volume of golf ball 101.

Mantle Layer Properties

In some embodiments, the mantle layer may be harder than the cover of agolf ball. For example, in some embodiments, mantle layer 45 may have ahigher hardness than cover 20 of ball 101. In some embodiments, mantlelayer 45 may have a Shore D hardness of greater than about 60 while thecover 20 may have a Shore D hardness of less than about 60. In someembodiments, mantle layer 45 may have a hardness of between about 62-70,while cover 20 may have a Shore D hardness of from about 45-58 asmeasured on the ball. In some embodiments, the hardness differencebetween mantle layer 45 and cover 20 may be at least about 4 Shore Dunits, where mantle layer 45 is harder than cover 20. Providing a softercover 20 and a relatively hard mantle layer 45 may reduce the spin offof driver shots due to the hard mantle layer 45 while allowing ironshots to attain high or desired spin rates due to the soft cover 20.

In some embodiments, mantle layer 45 and cover 20 may have a similarspecific gravity. In some embodiments, the specific gravity of mantlelayer 45 and cover 20 may be about 1.2. In some embodiments, mantlelayer 45 may have a specific gravity of about 1.160 (for example1.160+/−0.005) and cover 20 may have a specific gravity of about 1.150(for example 1.150+/−0.02). In some embodiments, mantle layer 45 mayhave a specific gravity of 1.160.

Mantle Layer Materials

Mantle layer 45 may be formed of any suitable material with which theproperties discussed above may be achieved. In some embodiments, mantlelayer 45 may be urethane or urethane based.

Alternative Mantle Layer Configuration

FIG. 4 shows a ball 201 having a structural configuration similar toball 200 in FIG. 2. Accordingly, components of ball 201 may havedimensions, properties, and/or characteristics that are the same orsubstantially similar to corresponding components of ball 200, which, asdiscussed above, may be substantially similar to the components ofFIG. 1. In ball 201, like ball 200 in FIG. 2, the enclosing layer 80 isdisposed radially outward of intermediate layer 70, as shown in FIG. 4.In addition, as also shown in FIG. 4, ball 201 may further include amantle layer 85. Mantle layer 85 may be disposed between enclosing layer80 and cover 60. That is, mantle layer 85 may be disposed radiallyoutward of enclosing layer 80 and radially inward of cover 60, as shownin FIG. 4. Mantle layer 85 may have the same or substantially similardimensions (thickness), properties, and characteristics as mantle layer45 discussed above, with adjustments made to accommodate its moreradially outward location.

Examples

Tables 1 to 5 below illustrate exemplary compositions for the variouscomponents of golf balls having structures in accordance with thepresent disclosure. As indicated in Table 5, Examples 1 and 2 andComparative Examples 1 and 2 include 24 mm cores, whereas Examples 3 and4 and Comparative Examples 3 and 4 include 28 mm cores. In addition,Examples 1 and 3 correspond to an embodiment having a configuration likethat shown in FIG. 1, in which the enclosing layer encloses the core,but is disposed radially inward of the intermediate layer, as indicatedin the “Enclosing Layer” portion of Table 5. Examples 2 and 4 correspondto an embodiment having a configuration like that shown in FIG. 2, inwhich the enclosing layer is disposed radially outward of theintermediate layer, as also indicated in the “Enclosing Layer” portionof Table 5.

As indicated in Table 5, it will be noted that the cores of Examples 1and 3 maintains a higher COR when the ball is exposed to cool weatherthan the cores of Comparative Examples 1 and 3, which do not include anyinsulating, enclosing layer. Thus, as indicated in Table 5, the COR of amultilayer solid golf ball with enclosing layer 40 will drop slower in acold environment than the conventional multilayer golf ball without theenclosing layer, demonstrating that the multilayer solid golf ball 100of the present invention has the higher COR in a cold environmentthereby providing a longer flying distance and a better ball control.

Examples 2 and 4 in Table 5 are balls configured according to theembodiment shown in FIG. 2. When compared with Comparative Examples 2and 4, the data for Examples 2 and 4 demonstrates that the COR of ball200 with enclosing layer 80 will drop slower in a cold environment thana conventional multilayer solid golf ball without the enclosing layer,such as Comparative Examples 2 and 4. Thus, ball 200 will maintain ahigher COR in a cold environment, proving a longer flying distance andbetter ball control.

Table 5 includes calculated data, for each example, of the ratio betweenthe ball COR after exposure to 0° C. for 30 minutes to the original CORat 24° C. As shown in Table 5, the ratio for each of Examples 1-4 is0.944 (94.4 percent) or greater. Thus, a ball having an insulating layeraccording to the present disclosure has a COR after exposure to 0° C.for 30 minutes that is at least 94.4 percent of the original COR at 24°C. In contrast, for each of Comparative Examples 1-4 (without aninsulating layer), the ratio is less than 0.944.

TABLE 1 Core Resin Blend A HPF 2000* 100 *HPF 2000 is trade name ofionomeric resin by E. I. DuPont de Nemours and Company

TABLE 2 Intermediate Layer Rubber Compound B C TAIPOL BR0150* 100 100Zinc diacrylate 28 26 Zinc oxide 6 4.5 Barium sulfate 39.5 32 Peroxide 11 *TAIPOL BR0150 is the trade name of rubber by Taiwan Synthetic RubberCorp.

TABLE 3 Enclosing Layer D E Methyl ethyl ketone 31 33 Methyl cyclohexane57 58 ethylene vinyl acetate 12  9

TABLE 4 Cover Resin Blend F Surlyn ® 8940* 50 Surlyn ® 9910* 50*Surlyn ® 8940 and Surlyn ® 9910 are trade names of ionomeric resin byE. I. DuPont de Nemours and Company

TABLE 5 Example Comparative Example 1 2 3 4 1 2 3 4 Core Blend A A A A AA A A Diameter (mm) 24 24 28 28 24 24 28 28 Weight (g) 7.0 7.0 11.1 11.17.0 7.0 11.1 11.1 Specific gravity 0.96 0.96 0.96 0.96 0.96 0.96 0.960.96 Surface Shore D hardness 53 53 53 53 53 53 53 53 Compression,10-130 kg 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 (mm) Core COR* 0.8471 0.84740.8459 0.8461 0.8472 0.8474 0.8460 0.8459 Intermediate Layer Compound CC B B C C B B Diameter (mm)** 39.3 39.3 39.3 39.3 39.3 39.3 39.3 39.3Weight (g)** 36.8 36.8 36.8 36.8 36.8 36.8 36.8 36.8 Specific gravity(g/cm³)** 1.17 1.17 1.17 1.17 1.17 1.17 1.17 1.17 Surface Shore Dhardness 41 41 43 43 41 41 43 43 Compression, 10-130 kg 3.3 3.3 3.2 3.23.3 3.3 3.2 3.2 (mm)** Enclosing Layer Blend E E D D None None None NoneThickness (mm) 0.02 0.02 0.02 0.02 — — — — Thermal conductivity 0.120.12 0.10 0.10 — — — — (W/m-K)*** Enclosing core Yes — Yes — — — — —Enclosing intermediate — Yes — Yes — — — — layer Cover Blend F F F F F FF F Thickness 1.71 1.71 1.71 1.71 1.7 1.7 1.74 1.74 Specific gravity0.99 0.99 0.99 0.99 0.99 0.99 0.99 0.99 Surface Shore D hardness 69 6969 69 69 69 69 69 Ball Weight (g) 45.4 45.4 45.4 45.4 45.4 45.4 45.445.4 Diameter (mm) 42.7 42.7 42.7 42.7 42.7 42.7 42.7 42.7 Compression,10-130 kg 2.8 2.8 2.9 2.9 2.8 2.8 2.9 2.9 (mm) Ball COR* 24° C. 0.81010.8105 0.8123 0.8124 0.8112 0.8110 0.8128 0.8132 0° C. × 10 mins 0.78280.7825 0.7871 0.7830 0.7751 0.7781 0.7795 0.7804 0° C. × 20 mins 0.77170.7713 0.7789 0.7748 0.7648 0.7683 0.7712 0.7720 0° C. × 30 mins 0.76630.7660 0.7736 0.7685 0.7601 0.7635 0.7667 0.7670 30 min COR/24° C. COR0.946 0.945 0.952 0.946 0.937 0.941 0.943 0.943 *For the COR test of thepresent invention, the initial velocity is 40 m/sec. **Value of core +intermediate layer + enclosing layer. ***Thermal conductivity ismeasured by a thermal conductivity analyzer, Hot Disk TPS 2500 with thinfilm module, commercially available from Hot Disk AB company, Sweden.

While various embodiments of the invention have been described, thedescription is intended to be exemplary, rather than limiting and itwill be apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof the invention. Accordingly, the invention is not to be restrictedexcept in light of the attached claims and their equivalents. Also,various modifications and changes may be made within the scope of theattached claims.

1-20. (canceled)
 21. A method for making a multilayer golf ball,comprising: forming a solid core from a highly neutralized polymer;forming a enclosing layer around the core, the enclosing layer being asolid material having a thickness of 0.01 mm to 0.4 mm, the solidmaterial comprising ethylene vinyl acetate copolymer; and providing acover surrounding the enclosing layer to form the golf ball; wherein athermal conductivity of the enclosing layer is less that a thermalconductivity of the cover.
 22. A method according to claim 21, whereinthe thermal conductivity of the enclosing layer is 0.12 W/m-K or less.23. A method according to claim 21, wherein the solid material of theenclosing layer is formed from a mixture of ethylene vinyl acetatecopolymer, methyl ethyl ketone, and methylcyclohexane.
 24. A methodaccording to claim 21, wherein the thermal conductivity of the enclosinglayer is such that after exposing the golf ball to air of 0° C. for 30minutes the golf ball has a coefficient of restitution that is at least94.4 percent of a coefficient of restitution of the golf ball before theexposing.
 25. A method according to claim 21, wherein the enclosinglayer has a thickness of about 0.02 mm.
 26. A method according to claim21, further comprising forming an intermediate layer around the corebefore forming the enclosing layer around the intermediate layer and thecore, or forming the intermediate layer around the enclosing layer andthe core, wherein the intermediate layer is formed of a solid materialand a thermal conductivity of the intermediate layer is greater than thethermal conductivity of the enclosing layer.
 27. A method according toclaim 21, wherein the solid material of the enclosing layer consistsessentially of the ethylene vinyl acetate copolymer.
 28. A methodaccording to claim 21, wherein the enclosing layer is formed directly incontact with the core.
 29. A multilayer golf ball, comprising a solidcore, a solid enclosing layer comprising ethylene vinyl acetatecopolymer, and a cover, wherein the multilayer golf ball is formed bysteps of: forming the solid core from a highly neutralized polymer;forming the enclosing layer around the solid core, the enclosing layerbeing formed of a solid material and having a thickness of 0.01 mm to0.4 mm; and surrounding the enclosing layer with the cover, therebyproviding the golf ball; wherein a thermal conductivity of the enclosinglayer is less that a a thermal conductivity of the cover.
 30. Amultilayer golf ball according to claim 29, wherein the thermalconductivity of the enclosing layer is 0.12 W/m-K or less.
 31. Amultilayer golf ball according to claim 29, wherein the thermalconductivity of the enclosing layer is such that after exposing the golfball to air of 0° C. for 30 minutes the golf ball has a coefficient ofrestitution that is at least 94.4 percent of a coefficient ofrestitution of the initial golf ball before the exposing.
 32. Amultilayer golf ball according to claim 29, wherein the enclosing layerhas a thickness of about 0.02 mm.
 33. A multilayer golf ball accordingto claim 29, further comprising an intermediate layer formed around thecore wherein the intermediate layer is in direct contact with the coreand the enclosing layer is in direct contact with the intermediatelayer, or an intermediate layer formed around the core and the enclosinglayer wherein the enclosing layer is in direct contact with the core andthe intermediate layer is in direct contact with the enclosing layer,and wherein a thermal conductivity of the intermediate layer is greaterthan the thermal conductivity of the enclosing layer.
 34. A multilayergolf ball according to claim 29, wherein the solid material of theenclosing layer consists essentially of the ethylene vinyl acetatecopolymer.
 35. A multilayer golf ball according to claim 29, wherein theenclosing layer is directly in contact with the core.